Lubricating compositions containing metal salt of a bicyclo carboxylic acid



United States Patent 3,223,632 LUBRIQATING COMPOSITIGNS CGNTAINTNGlliEl'lgdL SALT 0F A BICYCLO (JARBOXYLIC Hans G. Vesterdai, Elizabeth,and Rudolph Kassinger,

Westiield, NJ, assignors to Esso Research and Engineering Company, acorporation of Delaware No Drawin Filed Mar. 22, 1963, Ser. No. 267,3571 Claim. (Cl. 252--33.6)

This invention relates to lubricating compositions. In one aspect itrelates to lubricating greases and concentrates containing metal salt ofa bicyclo carboxylic acid. It also relates to the methods of preparationof these greases and concentrates. In a very specific aspect thisinvention relates to a fire resistant lubricant formed by thickening asilicone fluid with an alkaline earth metal salt of a halogenatedbicyclo dicarboxylic acid.

Lubricating greases capable of operating under extreme pressure loadingconditions and at temperatures above 400 F. are required in manyoperations, e.g., lubrication of aircraft, rocket engines, steel makingfacilities, etc. Many commercially available lubricants are not capableof functioning under these extreme conditions. Moreover, many of thosecommercially available lubricants present fire hazards, i.e., they areflammable.

DISCOVERY It has now been discovered, and this discovery forms the basisof the present invention, that lubricating oils, e.g., silicone fluids,may be effectively combined with metal salt of certain bicyclocarboxylic acids. These salt-containing lubricating compositions areeffective both as extreme pressure and anti-wear additives in otherlubricants, and as greases, per se. It will be realized, of course, thatthe relative proportion of the salt and lubricating oil will varyconsiderably, depending upon the ultimate use of the composition. Forexample, it has been found that lubricating greases containing thesesalts as substantially the only thickener will generally contain fromabout 38 to 82 wt. percent, e.g., 46 to 75 wt. percent of the salt basedon the total formulation weight of the grease. it, however, it isdesired to use these compositions as lubricant additives or incombination with other thickeners, etc., it is generally moreadvantageous to use from about 0.5 to 46 wt. percent, usually 2 to 35wt. percent, e.g. 4 to 25 wt. percent of the salts based on the totalformulation weight of the resulting composition. it should beunderstood, however, that depending upon the consistency of thecomposition desired and the properties required less than 0.5 Wt.percent or more than 82 wt. percent of the salt of the bicyclo acid maybe employed.

It has been further discovered that these salts of bicyclo carboxylicacids may be advantageously used in combination with other thickeners,especially the metal salts of benzoic acid (which have recently beendiscovered to be effective in this respect). This is particularly truewhen it is desired to use the composition, per se, as a grease. Otherauxiliary thickeners for use in the novel lubricating compositions ofthe present invention include the fatty acid soaps, carbon black, copperphthalocyanine, ammeline, indanthrene blue, polyaryl ureas, etc. WhenICC used in combination with the salts of benzoic acid (which arepreferred for certain applications) or other auxiliary thickeners, thecombined amount of thickener (e.g., bicyclo dicarboxylic acid salt plusbenzoic acid salt) will generally range from 5 to 82 Wt. percent, moreusually from 15 to wt. percent, e.g., from 20 to 50 wt. percent etc.When used in combination with other thickeners, the bicyclo acid saltswill generally be present in amounts of from 2 to 35 wt. percent, e.g.,from 4 to 25 wt. percent based on the total formulation weight of thegrease.

We do not, however, mean to limit ourselves to the use of the bicycloacid salts, alone, or in combination with benzoic acid salts. Ourinvention resides in the fact that lubricating oils, particularly thesilicone oils, may be effectively combined with metal salt of variousbicyclo dicarboxylic acids to form novel lubricating compositions whichcan be used, per se, as lubricants, or as additives in other lubricatingcompositions. The particular combination of this lubricating composition(bicyclo acid salt plus oil) with benzoic acid salt, e.g., calciumbenzoate, has been shown to illustrate the additive eitect of thesenovel compositions and because that particular combination produces alubricant having certain desirable proper ties.

Lubricating compositions, e.g., greases, prepared according to thepreferred form of the present invention will usually have a longlubrication life in high speed bearings operating at, for example,10,000 rpm, and will function within the broad temperature range of fromabout -65 F. to 500 F. Additionally, these preferred greases may be usedfor shorter periods of time at temperatures of up to 700 F. Moreover,these preferred greases are fire resistant and are particularly suitedfor lubrication in places where there is a danger of fire such as kilncars, oven hinges, electrical switches, etc.

BICYCLO CARB OXYLIC ACIDS The bicyclo carboxylic acids which arecontemplated for use according to the present invention include thebicyclo dicarboxylic acids (or their anhydrides) represented as follows:

wherein X represents an atom of hydrogen, chlorine, fluorine, bromine oriodine. The Xs may be the same or different. It is preferred that all ofthe Xs be halogen atoms, and more preferably, that all be chlorine. Whenall of the Xs are chlorine, the acid is known as chlorendic acid and canbe identified as 1,4,5,6,7,7-hexachlorobicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic acid.

This acid can be prepared in its anhydride form by reactinghexachlorocyclopenta-1,3-diene with maleic anhydride. The preparation ofthese bicyclo dicarboxylic acids does not constitute a part of thepresent invention. However, they may be prepared by the Diels-Alderaddition of the corresponding halogenated cyclopentadiene and maleicanhydride. Chlorendic acid is commercially available from the HookerChemical Company, Niagara Falls, New York. This acid was used in theworking examples of the present invention and is often referred to asHET acid. The use of this acid in the examples is for purposes ofillustration only, and the present invention should not be limitedthereby.

While the bicyclo acids of the type just described are all believed tobe effective, it is not to be implied that all serve with equalefficiency, since the efliciency of the various compounds will vary tosome extent depending upon the nature and severity of the service towhich they are subjected as well as their inherent differences inchemical structure.

METAL COMPONENTS OF THE SALTS Although other metals may be used, e.g.,Fe, the metal component of the salts should preferably be an alkalimetal or alkaline earth metal, viz, Na, K, Li, Ca, Sr, etc. Of thesemetals, the alkaline earth metals are the more preferred and calcium isespecially preferred. These metals may be conveniently used is suchforms as their hydroxides, etc., e.g., hydrated lime.

It is surprising to note that when diesters of the previously describedbicyclo carboxylic acids are employed (rather than the metal salts ofthe present invention) solid lubricating compositions do not result. Forex ample, US. Patent No. 2,771,423 describes cutting oils containing upto 75 wt. percent of the C -C alcohol diesters of chlorendic acid. US.Patent No. 2,985,644 describes sulfurized esters of chlorendic acidwhich are oil soluble and can be used in cutting oils in amounts up to35 wt. percent.

SUITABLE LUBRICATING OI LS The lubricating oil base stock selected foruse in the present invention is preferably a lubricant of the type whichis, per se, best suited for the particular use for which the ultimatelubricating composition is designed. Since many of the propertiespossessed by lubricating oil are imparted to the ultimate lubricatingcomposition, it is advantageous to employ an oil which is, itself,thermally stable at the contemplated temperature of lubrication.

The more preferred lubricating oils for use according to the presentinvention are the silicone fluids. They are particularly preferredbecause of their high thermal stability and compatibility with the saltsof the present invention. Moreover, the preferred greases prepared fromthese fluids are fire resistant.

The silicone fluids which can be effectively used in the presentinvention include those silicone fluids having a viscosity of about 1 to500, e.g., 30 to 400, centistokes at 100 F. although it may sometimes bedesirable to use fluids having a viscosity outside of these ranges.These fluids are poly organo siloxanes having the general formula:

wherein R is an alkyl, aryl, alkaryl, aralkyl or hydrogen radical. TheRs need not be the same. Generally n is an integer of from about 2 to 50or more, e.g., 6 to 35. The particular value of n is not critical aslong as the fluid has the desired properties, e.g., viscosity, etc.Particular materials which have been found to be especially suited forthe present invention are silicone fluids QF-6- 7012 and QF-67024 whichare products of the Dow Corning Company, Midland, Michigan. These fluidsare the most preferred base oils for use in the present invention. Theyare both polymethylphenyl siloxanes having the general formulapreviously indicated. QF6 7012 is a medium polymethylphenyl siloxane.QF-6- 7024 is a high viscosity silicone fluid which has a lowervolatility than QF-6-7012 and is, therefore, better suited 4 for hightemperature operation. The pour point of QF-6-7024 (+25 F.) makes itless suitable, however, for low temperature operation than QF67012 whichhas a pour point below minus F. Inspections obtained on these fluids areshown in Table I below.

TABLE I.-SILICONE FLUIDS QF-fi-7012 AND QF-fi-7024 Viscosity 100 F.(cs.) 64. 3 225. 4

Viscosity 210 F. (cs) 21. 2 20. 40

Viscosity Index (IOU-210 F.) 162 109 Evaporation Loss 400 F. (wt.percent after 0. 5 0.2

24 hrs). l00 +25 Pour Point F) According to the preferred form ofpresent invention, a bicyclo carboxylic acid (in the presence or absenceof an auxiliary thickening agent or its precursor, e.g., benzoic acid)is mixed with a lubricating oil, e.g., silicone flud, and usually heatedto from 300 to 500 F., preferably above 350 F., at which point asuitable alkali or alkaline earth metal base is added, e.g., hydratedlime. Although neutralization may be accomplished at lower temperatures,e.g., 100 F., it is preferred that the neutralization of the bicycloacid be done above 350 F. and even more preferably at 400 F. or higher.This high temperature neutralization improves the texture of the finalgrease and seems to enhance the thickening effect of the bicyclo acidsalt. Additional heating (if required) and mixing is performed until thetemperature reaches from about 375 to 500 F. The mixture is then cooledto, for example, 250 F. At this point, various additives, e.g., phenylalpha naphthylamine, p,p-dioctyldiphenyl amine, dipyridylamine, etc.,may be added, if desired. The mixture is then cooled to, for example,from about 100 F. to F. and milled. The additional heating after themetal base, e.g., hydrated lime, was added is required to remove thewater of reaction. Optionally, and much less preferably, the water ofreaction may be allowed to remain in the grease to form a cold-settlubricant. This latter choice is not recommended where the grease is tobe used above about 250 F. As another alternate, the metal salt may bepreformed and added to the oil although this technique is not nearly aseffective as the in situ technique.

As indicated, the lubricating compositions of the present invention maycontain other lubricant additives, if desired, to improve specificproperties of the lubricant without departing from the scope of thepresent invention. Thus, the lubricating compositions of the presentinvention may optionally contain corrosion and rust inhibitors, extremepressure agents, anti-oxidants, dyes, etc. Whether or not such additivesare employed, and the amounts thereof, depend to a large extent upon theseverity of the conditions to which the composition is subjected andupon the original stability of the lubricating oil base. When suchconventional additives are used, they are generally added in amountsbetween about 0.001 and 10 wt. percent or more based on the weight ofthe total composition.

The terms alkalinity and acidity as used herein refer to thosephenomenon which are determined as follows: ten (10) ml. of 0.5 N HClare added to a ten (10) gm.

charge of grease sample which is slurried in one hundred (100) ml. ofnaphtha and fifty (50) 1ml. of ethanol. This is then back-titrated with0.5 N NaOH to a phenolphthalein end point. The results are thencalculated and reported as percent NaOH or oleic acid. It is preferredthat the maximum alkalinity be no more than about 0.40% and preferablythat the lubricating compositions be substantially neutral. Even morepreferably, the compositions are slightly acidic. This seems to enhancethe effect of amine-type oxidation inhibitors. The effect isparticularly pronounced in the case of silicone fluids.

EXAMPLES The present invention will be more clearly understood byreference to the following examples which include a preferredembodiment. All parts are by weight unless otherwise indicated.

Example 1 Six hundred parts of l,4,5,6,7,7 -hexachlorobicyclo(2.2.1)-hept-5-ene-2,3-dicarboxylic acid (hereinafter referred to as HETacid) were mixed with 240 parts of Dow Corning silicone fluid QF-6-7024(a polyphenylmethyl siloxane) and rapidly heated in a grease kettle to400 F. At 400 F. the acid formed a gel like mixture with the siliconefluid. One hundred sixty parts of hydrated lime were slowly added to thegel like mixture. Heating and mixing were continued for about 45 minutesas the reaction between the hydrated lime and HET acid progressed. Alarge part of the water of reaction was flashed during this time anddehydration was completed by soaking the reaction mixture at 300 F.until steam evolution subsided. The remaining mass was cooled to 110 'F.One hundred parts of silicone fluid QF-6-7024 were added to the mass atthis point and the product was milled. The resulting composition had anexcellent grease structure and its properties and formulation are shownin Table II.

Example 2 Two hundred ninety-four parts of silicone fluid QF-6- 7012were mixed with 180 parts of benzoic acid and 60 about minutes until allof the water of reaction had been evaporated. Thirteen parts ofp,p-dioctyldiphenyl amine and 19 parts of phenyl alpha naphthylaminewere added after the mass had cooled to 250 F. The mass was then rapidlycooled to 110 F. and milled in a rolling mill. The finished grease had atested acidity of 4.3% calculated as percent oleic acid. The resultinglubricant had the formulation and properties as shown in Table II.

Example 3 To later show the additive efiect of the metal salts of thebicycle acids, a test control grease was prepared as follows:

Two hundred forty parts of benzoic acid were mixed with 264 parts ofsilicone fluid QF-6-7012 and heated with mixing to 250 F. Sixty-sixparts of hydrated lime and 285 parts of silicone fluid were added tothis mixture while heating to 300 F. The resulting mass was then heatedto 375 F. The heating was continued at that temperature for 1 hr. untilthe water of reaction had evaporated. The mass was then cooled to 250 P.where 26.6 parts of phenyl alpha naphthylamine and 17.7 parts ofp,p'-dioctyldiphenyl amine were added. The mass was then rapidly cooledto 110 F. and milled in a Morehouse mill at a clearance at 0.001 inch.The formulation and properties of this lubricating composition are shownin Table II.

Example 4 To illustrate the efiectiveness of the calcium salt of HETacid as an extreme pressure additive, a lubricating grease was preparedby blending with a spatula and then milling in a laboratory greaseworker (at ambient conditions) 47 parts of the lubricating compositionof Example 1 with 260 parts of the test control grease of Example 3 and114 parts of a silicone fluid (QF-6-7012). The resulting mixture wasmilled and tested. It had an alkalinity of 0.06%, calculated as percentNaOH (based on the weight of the finished grease). The grease thusprepared had the approximate formulation and properties as shown inTable II.

TABLE II Initial Charge Formulation (weight percent) 1 Example 1 Example2 Example 3 Example 4 1 l. Silicone fluid 69.5. 2. Bicyclo dicarboxylicacid 4 7.42. 3. Benzoic acid 4 20.0. 4. Hydrated lime 5. Phenyl alphanaphthylamine 1.85. 6. P,p-dioctyldiphenyl amine 1.23. Properties:

1. Appearance Excellent, Smooth. Gray. Smooth. 2. ASTM penetration 77 F(mm./10)

Unworked 315 281. Worked 60X... 356 288. 3. ASlM dropping point, F 500+500+ 500+ 500+. 4. Extreme pressure values (mean Hertz load)- (a) EPvalue (kg) 84.6 39.0 21.1 29.7. (b) Weld point (kg) No weld point 315.

5. 4-Ball wear (scar dia., mm.) 5 6. AlgEgdgLGI Lubrication Life (10,000r.p.m. 450. 566+.

u, rs. 7. Flammability Wont burn in open flame, carbonizes and glows.

1 Actual values in grease are somewhat different due to loss of water.

1 True formulation of grease.

3 Added to the finished grease.

4 Present as the calcium salt.

5 Steel on steel, 10 kg., 75 0., 1 hr., 1800 r.p.m.

It can be seen from Table II that the lubricating composition of Example1 had some very desirable properties, viz, a smooth texture, a highdropping point, an extremely high weld point, excellent wearcharacteristics (when compared to the base oil, per se, which had a scardia. of

about 400 F. Heating was continued at 400 F. for about 2.0 mm.), and wasnon-flammable. When exposed to the open fiame of a Bunsen burner, itwould not support fire, but merely carbonized and glowed. This lattercharacteristic would be particularly useful where fire presents aproblem, e.g., near blast furnaces, etc. Note that this unique lubricantdoes not require the use of secondary or auxiliary thickeners. Thelubricant of Example 2, which contained calcium benzoate, was a hardergrease having a good lubrication life. The test control grease ofExample 3 does not contain any bicyclo acid salt. It has a goodlubrication life, but the very poor extreme pressure properties whichare characteristic of the silicone base oil. The addition of thelubricating composition of Example 1 to the test control grease ofExample 3 produced the very much improved grease of Example 4. While thelubrication life decreased, it was still quite high. More importantly,however, the extreme pressure properties were substantially increased.This is very important since most applications are in loaded bearings.Many commercially available products of similar purpose, price, etc.,have a good lubrication life at no load, but a very poor life under evenminimal loading conditions. Note the surprising increase in load thatthe new composition could endure without reaching a weld point. Thus, itcan be seen that lubricating compositions prepared according to thepresent invention have very desirable extreme pressure properties.

Having thus described our invention with a certain degree ofparticularity, it will be realized that numerous modifications andadaptations may be made within the spirit and scope of the invention ashereinafter claimed.

We claim:

A soap-free lubricating grease comprising a silicone lubricating fluid,as the base oil, and an amount sufficient to form a grease structure andwithin the range of from 20 to 65 wt. percent of a mixture of calciumsalts of chlorendic acid and benzoic acid, the amount of calcium salt ofsaid chlorendic acid being about 4 to 35 wt. percent of the totalweightof said grease.

References Cited by the Examiner UNITED STATES PATENTS 2,132,137 12/1939Ricketts 252-41 2,880,174 3/1959 Morway et al 25239 2,976,242 3/1961Morway 25239 3,113,849 12/1963 McCoy 44-7 OTHER REFERENCES HET Acid,Bulletin No. 40, July 1954, Hooker Electrochemical Co., New York, page3.

HET Acid, Bulletin No. 40, July 1954, Hooker Electrochemical Co., NewYork, page 4.

DANIEL E. WYMAN, Primary Examiner.

